¿Cuánto contamina un par de vaqueros? Hacia un denim sostenible

Mar 8, 2022 | GreenWeave

The jeans market and environmental damage: how to produce sustainable denim

A pair of jeans? That’s 11 thousand liters of water, thank you. And this is enough to understand that denim production is currently not sustainable.

Look inside your closet: how many jeans do you see? Now, consider that for each pair between 7 and 11 thousand liters of water were used, 11 thousand liters! More than it takes to produce a kilo of beef. An impressive amount, isn’t it? And this water could be used in better ways. But how can you do without jeans? You can’t. That is why we are also looking for a solution to reduce pollution and waste caused by the processing of denim, thus making its production sustainable.

Jeans or Denim?

First of all, a bit of clarity: what is the difference between jeans and denim? For the uninitiated, denim is the fabric composed mainly of diagonally woven cotton and therefore very robust. It often includes a variable percentage of polyester, nylon, lyocell or elastane. It was born around the fifteenth century in France and more precisely in the city of Nîmes, from which it takes its name: de-Nîmes, denim. It is used to make jackets, shirts, vests, shoes, bags… and our beloved jeans. Jeans are a style of trousers, an item of clothing that appeared in the second half of 1500 in Genoa and brought to global success by Levi Strauss in 1853. Now that we have revealed this mystery, let’s deal with the real problem: why is denim processing so harmful to the environment? Why does it take so many liters of water to produce a pair of jeans? To answer these questions, we must ask ourselves another fundamental one: how is denim dyed?

La colorazione dei jeans e i danni ambientali: verso un denim sostenibile - towards a sustainable denim

Indaco, leuco-indaco, indigofera: the colouring of jeans

Yes, it is true that in 11,000 liters per pair of jeans the cultivation of cotton and the entire treatment of denim to create jeans are included, but what causes the greatest waste of water is precisely the famous blue colouring, which has accompanied them since the Genoese origins, from where the blue canvas started, expanded and took hold with the name of blue jeans, from “blue de Genes”, blue of Genoa. But are jeans born blue? Of course not. As we said they are made of denim, which comes from cotton, so basically white. An organic molecule is used to make them blue: indigo. It’s naturally present in plants of the genus Indigofera and is intuitively blue, but as a pigment it is not soluble and therefore cannot be dissolved into water to proceed with the colouring of the fabric. So how can you do it? Indigo must be made soluble, and this can be done with chemicals that transform indigo into leuco-indigo, another molecule that is the soluble version of indigo. And guess what color is leuco-indigo? No, not blue, but yellow! And so this does not end here: once this yellow and soluble molecule has been obtained, it can be dissolved, and obviously a so-called solvent is needed: nothing threatening, just simple water. Denim is then immersed in an aqueous solution of leuco-indigo and subjected to several washes depending on how dark the fabric needs to be, turning yellow. Thanks to the oxidation in the air, the fabric finally takes on the blue colour as the air allows leuco-indigo to oxidize to indigo and adhere perfectly to the fiber. Finally you get the classic blue denim ready to become blue jeans.

Inquinamento produzione denim: acqua contaminata scaricata nel sistema idrico - verso un denim sostenibile

Blue jeans: the environmental aspect

This process has serious consequences for the planet: in addition to the cultivation of the cotton necessary to satisfy the jeans market, which requires enormous quantities of water itself, thousands of liters are used to wash the denim, and the water contaminated by chemicals is discharged into the water system, polluting rivers, seas and aquifers. In addition, fertilizers and pesticides are used for the intensive cultivation of cotton. According to an estimate made by Luiken et al., global jeans production exceeds 3,5 billion per year. If for each pair of jeans the water consumption is equal to 11,000 liters, it means that 38,5 trillion liters of water are needed to satisfy the total production of this popular garment. This is equal to more than 60 thousand times the annual water consumption of all China! If we add that about 3% of global irrigation water is used for the cultivation of cotton, it is certainly not surprising that the textile industry is considered responsible for 20% of the total hydro waste. Furthermore, the water discharged after washing contains dissolved leuco-indigo (which oxidizes to indigo over time) but especially indigo in suspension (so not dissolved), which turns waste sludge blue, as well as traces of the chemicals used for the transformation of indigo into leuco-indigo. This causes imbalance in various food chains of the aquatic ecosystem, as well as compromising the potability of water for us humans as well. This is what happens mainly in Asia, the world’s leading producer of denim with 70% of global production, but obviously has devastating consequences for the entire planet. So why continue with this system? It doesn’t make sense to us, and that is why our R&D team is looking for a solution to this problem. Ricerca e Sviluppo per un denim sostenibile

Towards sustainable denim

What we are working on is a process of recovering the indigo molecule from denim through a sustainable method. The goal is to separate the fiber from the dye, trying to get minimum consumption of solvent, aqueous or not, so as to be able to reuse both denim and dye.  We are running tests to find the right way to do it, a way that is not only effective but also sustainable from an environmental, energy, social and economic point of view. Sustainability is not something that is obtained on the fly, it requires careful and in-depth study as well as several attempts, but above all cooperation. For this we also turn to you, reader, whether you are operating in this sector or simply a person interested in the subject, because it is important that you are aware of the process and of the related problems to help us implement a solution that is beneficial for everyone. If you want to find out what you can do to support our research for sustainable denim, don’t hesitate: write to us at info@nazena.com or call us at 04441792229! Thank you   REFERENCES: Recovery and recycling of denim waste Luiken A, Bouwhuis G.   In: Denim: manufacture, finishing and applications. Woodhead Publications; 2015 Dyeing of denim yarns with non-indigo dyes M. Sanchez  Archroma, Castellbisbal, Spain Environmental impacts of denim K. Amutha  Bharathiar University, Coimbatore, India Water footprint of denim industry H. Pal1, K.N. Chatterjee2, D. Sharma3 1BPS Mahila Vishwavidyalaya, Sonipat, Haryana, India; 2The Technological Institute of Textile & Sciences, Bhiwani, India; 3Amity University Haryana, Gurgaon, India

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